How to create razor wire
Model a single segment of the wire and razor.



Create a curve object with the spiral shape you need (use the Add Curve: Extra Objects addon to create spirals) 



Add an array modifier to the wire/razor object 



and then add a curve modifier that uses the spiraled curve as object for the array. Then set the array modifier to use the curve. 



The original object and the curve remain editable, so you can shape them to fit your needs.

Here's the example file: